This invention is directed to an apparatus and method for processing image frames to decrease sensor artifacts in the image frames, more particularly to decrease sensor streaking artifacts in the image frames.
Many sensors for collecting data have anomalies in the sensors which cause artifacts in images output by the sensors. Typical of sensors which exhibit these properties are infrared sensors, i.e. IR sensors. Multi-detector parallel scanning IR sensors (including common module FLIR sensors and focal plane arrays) can induce sensory artifacts such as streaking into the image output of these sensors. The sensor artifacts degrade the performance of other downstream systems which utilize the output of the sensors.
The artifacts produced by the sensors are of varying origins. Artifacts are very noticeable for IR sensors during `warming up` of the sensors. However, individual elements in a multiple element sensor also change or drift over short periods of time even after the sensor is in a full operational mode. Additionally, response characteristics of individual sensor elements are also dependent upon the content of the scene which the sensor is detecting. For IR sensors very hot objects as, for instance, burning objects, engine compartments of vehicles, exhaust areas of vehicles and the like cause excessive streaking artifacts in data images obtained utilizing the IR sensor.
Temporal induced artifacts and hot spot induced artifacts are very difficult to remove utilizing filters which rely on measuring sensor response or filters which rely on the use of a large set of natural images or uniform test images. Artifacts would also degrade the effectiveness of time averaging filters which might utilize a large sequence of images over time to produce an optimal streak removal filter. Further, this last type of filter would require considerable computational requirements and image storage requirements for the production and storage of a sufficiently large number of images to serve as a basis for the filter. Also, by requiring the use of many sequential images for filtering purposes the ability to operate in real time or near real time is substantially compromised.
For a scanning sensor or a multiple element sensor, in theory it would be possible to have automatic gain circuits or other control circuits for each of the sensor elements and to adjust the circuits such that the output of every sensor element or sensor scan is equivalent. This, however, is not a practical solution because of the hardware demands and/or the inability of hardware or human operator to adjust the output of each sensor element or sensor scan to be totally equivalent to the output of all others.